576 research outputs found

    A 2 Earth Radius Planet Orbiting the Bright Nearby K-Dwarf Wolf 503

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    Since its launch in 2009, the Kepler telescope has found thousands of planets with radii between that of Earth and Neptune. Recent studies of the distribution of these planets have revealed a rift in the population near 1.5-2.0RR_{\bigoplus}, informally dividing these planets into "super-Earths" and "sub-Neptunes". The origin of this division is not well understood, largely because the majority of planets found by Kepler orbit distant, dim stars and are not amenable to radial velocity follow-up or transit spectroscopy, making bulk density and atmospheric measurements difficult. Here, we present the discovery and validation of a newly found 2.030.07+0.08 R2.03^{+0.08}_{-0.07}~R_{\bigoplus} planet in direct proximity to the radius gap, orbiting the bright (J=8.32J=8.32~mag), nearby (D=44.5D=44.5~pc) high proper motion star Wolf 503 (EPIC 212779563). We classify Wolf 503 as a K3.5V star and member of the thick disc population. We determine the possibility of a companion star and false positive detection to be extremely low using both archival images and high-contrast adaptive optics images from the Palomar observatory. The brightness of the host star makes Wolf 503b a prime target for prompt radial velocity follow-up, HST transit spectroscopy, as well as detailed atmospheric characterization with JWST. With its measured radius near the gap in the planet radius and occurrence rate distribution, Wolf 503b offers a key opportunity to better understand the origin of this radius gap as well as the nature of the intriguing populations of "super-Earths" and "sub-Neptunes" as a whole

    Fractalkine enhances oligodendrocyte regeneration and remyelination in a demyelination mouse model

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    Demyelinating disorders of the central nervous system (CNS) occur when myelin and oligodendrocytes are damaged or lost. Remyelination and regeneration of oligodendrocytes can be achieved from endogenous oligodendrocyte precursor cells (OPCs) that reside in the adult CNS tissue. Using a cuprizone mouse model of demyelination, we show that infusion of fractalkine (CX3CL1) into the demyelinated murine brain increases de novo oligodendrocyte formation and enhances remyelination in the corpus callosum and cortical gray matter. This is achieved by increased OPC proliferation in the cortical gray matter as well as OPC differentiation and attenuation of microglia/macrophage activation both in corpus callosum and cortical gray matter. Finally, we show that activated OPCs and microglia/macrophages express fractalkine receptor CX3CR1 in vivo, and that in OPC-microglia co-cultures fractalkine increases in vitro oligodendrocyte differentiation by modulating both OPC and microglia biology. Our results demonstrate a novel pro-regenerative role of fractalkine in a demyelinating mouse model

    A 2 R_⊕ Planet Orbiting the Bright Nearby K Dwarf Wolf 503

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    Since its launch in 2009, the Kepler telescope has found thousands of planets with radii between that of Earth and Neptune. Recent studies of the distribution of these planets have revealed a gap in the population near 1.5–2.0 R⊕, informally dividing these planets into "super-Earths" and "sub-Neptunes." The origin of this division is difficult to investigate directly because the majority of planets found by Kepler orbit distant, dim stars and are not amenable to radial velocity follow-up or transit spectroscopy, making bulk density and atmospheric measurements difficult. Here, we present the discovery and validation of a newly found 2.03^(+0.08)_(-0.07) R⊕ planet in direct proximity to the radius gap, orbiting the bright (J = 8.32 mag), nearby (D = 44.5 pc) high proper motion K3.5V star Wolf 503 (EPIC 212779563). We determine the possibility of a companion star and false positive detection to be extremely low using both archival images and high-contrast adaptive optics images from the Palomar observatory. The brightness of the host star makes Wolf 503b a prime target for prompt radial velocity follow-up, and with the small stellar radius (0.690 ± 0.025R⊙), it is also an excellent target for HST transit spectroscopy and detailed atmospheric characterization with JWST. With its measured radius near the gap in the planet radius and occurrence rate distribution, Wolf 503b offers a key opportunity to better understand the origin of this radius gap as well as the nature of the intriguing populations of "super-Earths" and "sub-Neptunes" as a whole

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

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    Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

    Search for heavy resonances decaying to two Higgs bosons in final states containing four b quarks

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    A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at root s = 8 TeV. The data correspond to an integrated luminosity of 19.7 fb(-1). The search considers HH resonances with masses between 1 and 3 TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t (t) over bar events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95 confidence level for the product of the production cross section and branching fraction sigma(gg -> X) B(X -> HH -> b (b) over barb (b) over bar) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0 TeV, significantly extending previous searches. For a warped extra dimension theory with amass scale Lambda(R) = 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55 TeV

    Search for supersymmetry in events with one lepton and multiple jets in proton-proton collisions at root s=13 TeV

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    Measurement of the top quark mass using charged particles in pp collisions at root s=8 TeV

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    Measurement of the Splitting Function in &ITpp &ITand Pb-Pb Collisions at root&ITsNN&IT=5.02 TeV

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    Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.Peer reviewe

    Measurement of nuclear modification factors of gamma(1S)), gamma(2S), and gamma(3S) mesons in PbPb collisions at root s(NN)=5.02 TeV

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    The cross sections for ϒ(1S), ϒ(2S), and ϒ(3S) production in lead-lead (PbPb) and proton-proton (pp) collisions at √sNN = 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, RAA, derived from the PbPb-to-pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, RAA(ϒ(1S)) > RAA(ϒ(2S)) > RAA(ϒ(3S)). The suppression of ϒ(1S) is larger than that seen at √sNN = 2.76 TeV, although the two are compatible within uncertainties. The upper limit on the RAA of ϒ(3S) integrated over pT, rapidity and centrality is 0.096 at 95% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date. © 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.Peer reviewe
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